MEANING AND REPRESENTATION OF BOUNDARIES IN KARST TYPE MAPS POMEN IN PREDSTAVLJANJE MEJA NA KARTAH KRASA

Transcription

1 ACTA CARSOLOGICA 30/ LJUBLJANA 2001 COBISS: 1.08 MEANING AND REPRESENTATION OF BOUNDARIES IN KARST TYPE MAPS POMEN IN PREDSTAVLJANJE MEJA NA KARTAH KRASA STEPHAN ANGSÜSSER 1 1 Lehrstuhl für Kartographie, Technische Universität München, Arcisstraße 21, D MÜNCHEN, GERMANY, angs@bv.tum.de, Internet: Prejeto / received:

2 Acta carsologica, 30/2 (2001) Izvle~ek UDK: 528.9: Stephan Angsüsser: Pomen in predstavljanje meja na kartah krasa Prispevek govori o mejah na splo{no in {e posebej o mejah na kartah krasa v velikem merilu. Predstavljen je metodolo{ki pristop, ki temelji na razlo~evanju odvisnih in neodvisnih spremenljivk. Na tem temelju je mogo~e zbrati podatke tako o tipu meje kot tudi o njeni natan~nosti. Ti dodatni podatki naj bi pomagali raziskovalcem odgovarjati na vpra{anja, povezana z nastankom krasa. Klju~ne besede: kartografija, speleokartografija, tipizacija krasa, tipi krasa, kra{ka tipolo{ka karta, meja. Abstract UDC: 528.9: Stephan Angsüsser: Meaning and representation of boundaries in karst type maps The paper deals with boundaries in general and specifically with boundaries in large scale karst type maps. On the basis of a differentiation into dependent and independent variables a methodological attempt is presented, allowing to integrate information about the boundary type and the boundary accuracy. This additional information should help karst researchers answering genetic questions. Key words: karst typification, karst types, karst type maps, boundaries, speleocartography, cartography. 196

3 Stephan Angsüsser: Meaning and representation of boundaries in karst type maps INTRODUCTION In numerous existing karst type maps boundaries are represented in a uniform way: thin unicolored (often black or grey) lines dividing different areas. For users of such maps it is not possible to get any further information about the boundary, e.g. criteria for and accuracy of the position. This is hardly a disadvantage in small scale maps because of generalisation needs. However, in large scale maps the situation is quite different. Here exists a greater potential to increase the amount of information about the karst types by differentiating the boundaries. The basic idea is not new. In 1982 for example Fink (Fink 1983, 232) drew a map of the Dürrenstein karst area (south of Lunz am See, at the border between Lower Austria and Styria, Austria). By using different kinds of line symbols a hierarchical system of nature types was established. In addition uncertainty of accuracy was shown at some segments of the boundary. GENERAL CHARACTER OF BOUNDARIES Boundaries are lines dividing different areas. The difference may occur in many respects, e.g. legal, structural or natural (after Witt 1979, 222). In the majority of cases the accuracy of a boundary between two administrative units is much higher than between two karst types. Different conditions of natural phenomena are often divided by a more or less wide transition zone than by a sharp line. For better understanding and comparing this kind of phenomena humans usually try to determine accurate boundaries anyhow. The arising problem is how to fix the boundary position. Presuming there are two areas with different values for a specific variable, accuracy of demarcation between them depends on two relationships: 1. value - space In connection with that relationship there are two facets. Magnitude of value change (Fig. 1) and abruptness of value change over a given distance (Fig. 2) between neighbouring areas (Burrough 1986, 120; Johnson et al. 1992, 108). Fig. 1: Accuracy of demarcation between two neighbouring areas: relationship value-space (magnitude of change). 197

4 Acta carsologica, 30/2 (2001) Fig. 2: Accuracy of demarcation between two neighbouring areas: relationship value-space (abruptness of change over a given distance). 2. value - time Value persistence over a given time period (Fig. 3) is necessary to find a stable boundary position. Fig. 3: Accuracy of demarcation between two neighbouring areas: relationship value-time (persistence over a given period). It is also important to notice that the mentioned relationships are both (spatial and temporal) scale dependent. MEANING OF BOUNDARIES IN KARST TYPE MAPS Meaning of boundaries in karst type maps is of course determined by the typification method. The choice for a specific method is influenced by several factors (Angsüsser 2000, 47): purpose of typification and visualisation scale (degree of conceptual generalisation) characteristics of the karst area available data available technologies economical considerations knowledge and skills of the participating persons

5 Stephan Angsüsser: Meaning and representation of boundaries in karst type maps Example: In the Dürrenstein area (mentioned above) a methodological attempt has been carried out to construct a karst type map at the scale of 1:25000 (Angsüsser 2000). The resulting map should help answering genetic questions (e.g. reasons for the occurrence of specific karst features or karst types) and is therefore conceived for karst researches. First it was necessary to define the term karst type. According to Trimmel a karst type is a karst area with an uniform and characteristic set of forms; it is formed by climatic, petrographic and tectonic factors (Trimmel 1965, 62; Fig. 4). Based upon that system a typification method has been developed. Available data were divided into two groups: dependent variables and independent variables. The first group consists of morphology (slope inclination, dolines, uvalas, corridors, cave entrances, dry valleys) and hydrology (streams, lakes, springs, ponors). Their values should be as homogeneous as possible in the delimited areas. The second group consists of rocks (petrography, lithology), tectonics (faults, joints) and superior morphology (slope inclination and slope aspect). The basic assumption is, where values of these factors are changing, there might perhaps be a good place for a boundary. No appropriate data were available for climate, soils, and vegetation. It is possible to treat the slope Fig. 4: Factors responsible for the development of karst landscapes and different karst types (after Trimmel 1998, 42). inclination as a dependent variable (part of karst features resp. areas) as well as an independent variable (influences the development of karst features resp. areas). Dikau has called this phenomenon dual character of relief (Dikau 1994, 100). The different variables were combined in form of an overlay of several analytical maps (cp. Grenzgürtelmethode (girdle method); e.g. Maull 1950; Witt 1970). More or less homogeneous areas were demarcated along significant changes (high magnitude and outstanding abruptness) of the independent variables` values. Favoured variables are the more time-stable ones (longer value persistence) like endogenous factors (rocks, tectonics). Using this method the following two main statements can be connected to the drawn boundaries. One about the kind of the underlying variable ( boundary type ) and one about significance of the value change of this variable ( boundary accuracy ). It must not be overlooked that there 199

6 Acta carsologica, 30/2 (2001) exists no proof about the relevance of the boundaries. But they can be helpful when formulating hypotheses about the distribution and genesis of different karst features and karst types. REPRESENTATION OF BOUNDARIES IN KARST TYPE MAPS For the representation of boundaries one can vary the cartographical variables (graphic-, timeand sound-related) for line and ribbon symbols. The decision for a specific kind of visualisation depends mainly on the same factors that influence the choice for a typification method (see above). Instead of conceptual generalisation the degree of structural generalisation (concerning geometry) is now scale dependent. Conventionally the graphic variables are the most important ones. Bertin discerns the following six: shape, orientation, colour hue, texture, lightness, and size (Bertin 1974, 74). The first two are hardly used to represent lines. The other four can be combined in different ways to communicate information about boundaries. Example: In the example stated above two main statements about the boundary could be made - one qualitative (type) and one quantitative (accuracy). The most adequate graphic variable to represent quality is colour hue. For boundaries based on geological change the colour magenta, for those based on slope aspect cyan and for those based on slope inclination green has been chosen (Fig. 5). Boundary accuracy at ordinal scale can be expressed by using texture, lightness as well as size. To achieve better legibility the variable size was used to construct transparent white ribbon symbols with three different widths to represent the three classes (Fig. 6). The so formed narrow areas along the line symbol allow for a better associativity with the transition zones being there in nature than using sharp lines. Fig. 5: Different line symbols for the representation of boundary types (after Angsüsser 2000, 138). Fig. 6: Different ribbon symbols for the representation of boundary accuracy (after Angsüsser 2000, 138). 200

7 Stephan Angsüsser: Meaning and representation of boundaries in karst type maps CONCLUSIONS The presented method shows the possibility to increase the amount of information in karst type maps by differentiating the boundaries. Considering this, additional variables can be integrated into the map. As a consequence new questions about the covered karst area can arise. This can be seen as a kind of quality feature of a map (Gartner 1999, 312). Contact karst is a boundary phenomenon. In this context it would be interesting to explore the influence of different boundary characteristics (which variables change, value-space and valuetime relationships) on the occurrence, distribution, shape and other properties of contact karst features. ACKNOWLEDGEMENT I want to thank Hofrat Dr. Karl Mais, Chief of Department of Karst and Caves, Museum of Natural History, Vienna, Austria, for motivating me to write this paper and my colleague mezzo professore Tumasch Reichenbacher for the correction. REFERENCES Angsüsser, St., 2000: GIS-basierte Erstellung einer Karsttypenkarte. Ein methodischer Versuch im Gebiet des Dürrensteins (Ybbstaler Alpen). Diplomarbeit betreut durch W. Kainz und Ch. Embleton-Hamann. Grund- und Integrativwissenschaftliche Fakultät, Universität Wien, 1-216, Wien. Bertin, J., 1974: Graphische Semiologie. Übersetzt und bearbeitet nach der 2. französischen Auflage (1973) von Jensch G., Schade D. & Scharfe W. - Walter de Gruyter, 1-430, Berlin. Burrough, P.A., 1986: Principles of Geographical Information Systems for Land Resources Assessment. - Oxford University Press, 1-194, Oxford. Dikau, R., 1994: Computergestützte Geomorphographie und ihre Anwendung in der Regionalisierung des Reliefs. - Petermanns Geogr. Mitt., Jg. 138, H. 2, , Justus Perthes, Gotha. Fink, M.H., 1983: Probleme der Typisierung des Hochgebirgskarstes in den Ostalpen. - Atti Convegno Internationale sul Carso di alta montagna (Imperia 1982), Vol. I, , Imperia. Gartner, G., 1999: Multimedia GIS and the Web. - In: Cartwright W., Peterson M.P. & Gartner G. (Eds.): Multimedia Cartography: Springer Verlag, New York. Johnson, C.A., Pastor J. & Pinay G., 1992: Quantitative Methods for Studying Landscape Boundaries. - In: Hansen A.J. & di Castri F. (eds.): Landscape Boundaries. Consequences for Biotic Diversity and Ecological Flows: Springer Verlag, New York. Maull, O., 1950: Die Bedeutung der Grenzgürtelmethode für die Raumforschung. - Zeitschrift für Raumforschung, Jg. 1950, H. 6/7, , Bonn. Trimmel, H., 1965: Speläologisches Fachwörterbuch (Fachwörterbuch der Karst- und Höhlenkunde). - Landesverein für Höhlenkunde in Wien und Niederösterreich, Wien. 201

8 Acta carsologica, 30/2 (2001) Trimmel, H. (Gesamtred.), 1998: Die Karstlandschaften der österreichischen Alpen und der Schutz ihres Lebensraumes und ihrer natürlichen Ressourcen. - CIPRA-Österreich, 1-119, Wien. Wiens, J.A., 1992: Ecological Flows Across Landscape Boundaries: A Conceptual Overview. - In: Hansen A.J. & di Castri F. (eds.): Landscape Boundaries. Consequences for Biotic Diversity and Ecological Flows: Springer Verlag, New York. Witt, W., 1970: Grenzlinien und Grenzgürtelmethode. - In: Arnberger, E. (Red.): Grundsatzfragen der Kartographie: Österreichische Geographische Gesellschaft, Wien. Witt, W., 1979: Lexikon der Kartographie (= Band B der Enzyklopädie Die Kartographie und ihre Randgebiete ). - Franz Deuticke, 1-707, Wien. POMEN IN PREDSTAVLJANJE MEJA NA KARTAH KRASA Povzetek Meje so ~rte, ki razmejujejo razli~na obmo~ja. Vendar so naravni pojavi razli~nih zna~ilnosti pogosteje lo~eni med seboj z bolj ali manj {irokim prehodnim pasom, kakor pa z ostro ~rto. Da pa bi vseeno nekako dolo~ili ustrezno mejo, moramo najti spremenljivko, katere vrednosti se v sosednjih regijah bistveno (signifikantno) razlikujejo. Ta signifikanca je lahko izra ena z odnosom vrednost-prostor (velikost in hitrost spremembe vrednosti) ali pa kot odnos vrednost-~as (vztrajanje - persistenca vrednosti). Oba odnosa pa sta odvisna od merila. Pomen meja na kartah tipov krasa seveda dolo~a metoda tipizacije. Primer, prikazan v prispevku, temelji na razdelitvi v skupine odvisnih spremenljivk (morfologija, hidrologija) in v skupine neodvisnih spremenljivk (kamnine, tektonika, morfologija povr{ja). Medtem ko naj bi bile vrednosti spremenljivk prve skupine v dolo~eni regiji ~im bolj homogene, so spremenljive vrednosti spremenljivk v drugi skupini tiste, ki dolo~ajo meje. Na podlagi zgoraj razlo enega lahko za vsak odsek meje dobimo dva podatka: prvi je kvalitativni (tip meje) in drugi kvantitativni (klasificirana natan~nost meje). Prvega predstavljamo z raznobarvnimi ~rtnimi simboli, drugega pa s simboli v obliki belih prozornih trakov v treh razli~nih {irinah. Predstavljena metoda nakazuje, mo nosti, kako pove~ati {tevilo informacij na kartah tipov krasa s podrobnej{o razmejitvijo. 202